I'm the first to admit that I've gone a bit "knife crazy" since discovering Bussekin knives in 2007; my current blade counts are:
Busse Combat: 105
Swamp Rat: 63
Scrap Yard: 159

The only used ones are those I bought that way in the secondary market + a green Swamp Warden I carried for a couple weeks before being told someone complained that I was carrying a weapon at work. I maintain an Excel Spreadsheet to track what I have, when I bought each of them and how much I paid (excluding shipping and taxes), largely so that my family would have some idea of what they're worth if anything were to happen to me. However, I wouldn't know how many knives I had or how much I'd spent on my hoard without it, so maintaining that documentation has been worthwhile on a personal level too.